This question does not require that sort of expertise. In fact, it could be

part of the problem: I am speaking about ordinary language, not technical

terms. What I am saying has a descriptive component and a normative one.

The descriptive one you are acknowledging by saying “people..referring to

everything in the lower reproductive tract as vagina.” I am making the empirical

claim that in addition to the use of the word “vagina” to refer to the part of the

body mentioned in the dictionary definition, the words is widely used to mean something broader.

And that meaning is even broader than the word vulva.

The normative component has to do with the attitude toward these usage facts (if they are facts).

My position is that standard usage is fine and should not be changed.

One could agree with me descriptively (as you seem to), but disagree with me on the normative

question. It is natural that an expert would prefer the technical terms over

common usage. To summarize, many words have both a strict meaning and broader meaning (species and genus).

“Vagina” is like that. Experts are helpful, yes. But they must be used with care. Your diagram is

great. I had a similar disagreement with you about the word “fetus”. It is standard usage pregnant

woman to speak of her baby, not her fetus. And there’s nothing incorrect about that.